SMTP, which is short for Simple Mail Transfer Protocol, is the software that enables you to send e-mail messages from your email addresses. Without it, you won't be able to use email applications or webmail. Every time you send an e-mail, your SMTP server connects to a DNS server to discover exactly where e-mails for the recipient domain are handled. Subsequently, it creates a connection to the remote email server and trades details. When the recipient mailbox is available, your server transmits the message to the receiving POP/IMAP server and the latter delivers that message to the specific mailbox where the receiver can get it. If you would like to send emails, you should always make sure that the website hosting company has the service with their packages. Even though you make use of online form that site visitors use to make contact with you, you'll still need an active SMTP server for your hosting account for the form to operate.